Poly(p-phenylene terephthalamide) (PPD-T) and poly(m-phenylene isophthalamide) (MPD-I) belong to a class of materials referred to as aramids. PPD-T fiber is well-known for its high strength and finds extensive use as reinforcement material in rubber, composites etc. MPD-I fiber is well-known for its fire resistance and is used, for example, in filter bags at electric power generation plants and protective clothing.
When exposed to moisture, acids or bases at elevated temperatures, aramid fibers will lose tenacity. For certain end-use applications, it is, therefore, desirable that the aramid fiber have greater resistance to hydrolysis. These applications include reinforcement for coolant hose in automobiles, oil-transport hose and belts. An object of the present invention is to obtain significant improvement in hydrolysis resistance of aramid fiber.